1. Field of the Invention
The present invention relates to a quick coupling for making a temporary junction between two pipes conveying a gas under pressure.
2. Brief Description of the Related Art
Conventionally, such a quick coupling comprises complementary male and female elements that are coupled together by engaging one in the other. The female element is generally coupled to an upstream pipe and is provided with a shutter member, which the male element moves towards an open position on being fully engaged in the female element. The male element is generally coupled to a downstream pipe. In order to ensure that during disconnection the male element is not expelled violently from the female element because of the pressure that exists in the downstream pipe, a locking mechanism for locking the male element in the female element can be designed in such a manner as to allow the male element to be fully released only after being placed temporarily in a position in which the downstream pipe is allowed to purge through the coupling. French patent application No. 1 503 989 describes such a locking mechanism, with the presence of such a mechanism in a coupling making the coupling safer to use.
Nevertheless, it can happen that while an operator is disconnecting pipes, the operator does not hold the locking mechanism long enough in its position for purging the downstream pipe, in which case the male element can still be ejected violently and dangerously from the female element.
European patent application No. 1 333 218 describes a coupling in which separation does not require one but rather two manual operations on a latch in order to reduce the risk of the male element being ejected violently. In addition to such operations being inconvenient, since they are performed successively, they also require the operator to wait, since these two operations must be separated from each other by another movement of the latch under drive from a return spring and triggered in a manner that depends on friction forces. Friction forces are themselves a function of several parameters that are difficult to control, such as the state of cleanliness of the coupling, so variation therein can lead to the unlocking operation taking place in random manner.
The invention has at least the object of further increasing the safety of quick couplings used for making a temporary junction between two pipes conveying a fluid under pressure.
To this end, the invention provides a quick coupling for making a temporary junction between upstream and downstream pipes conveying a gas under pressure, the coupling comprising a male portion and a female portion which comprises, firstly a hollow female element for receiving a male plug of the male portion, and secondly a latch for retaining a coupling element selected from the male plug and an optional adapter that is movable between a position for locking the male plug coupled in the female portion and a position for releasing the male plug, said latch being movable relative to the female element between a first position in which said latch is suitable for retaining the coupling element engaged to a first depth in the female portion and coupled in leaktight manner to said female portion, and a second position in which said latch is suitable for retaining the coupling element engaged to a second depth that is smaller than the first depth, the coupling including a passage for purging the downstream pipe to the outside when the coupling element is at the second depth, but not when the coupling element is at the first depth, the coupling being characterized in that said latch is configured in such a manner as to be returned towards its second position at least in part by positive pressure in said purge passage.